Why do you want to copy things into one of root's directories? This is potentially harmful and almost certainly unnecessary, so it would be better to find another way to achieve your end goal, whatever it is.
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PaulJun 15 '13 at 14:36

Sure thing. Don't tell us what you are trying to achieve. After all we are not trustworthy, aren't we? (Why are you asking us then?) And you have a right to shoot yourself in the foot.

Go ahead, here is your solution:

sudo ln -s /usr /user
sudo chown $USER -R /user/src # Like a BOSS!

Next time when the package manager wants to put new files into that directory or modify existing ones, well...

drwxr-xr-x 6 _BOSS_ root 4096 Jun 14 09:27 src/

booyah... permission denied

Why this is a bad idea

That directory is really named usr, it's not a typo and its permissions are not set like this to annoy you. This is all defined by a standard (FHS - Filesystem Hierarchy Standard) and the entire system with its programs and services relies on this structure to function properly. Therefore you do not change permissions and ownership or blindly copy stuff into there because some guide tells you to do so.

If you really need to copy source code manually to a location where the tools can pick it up, it is recommended to copy the source code to /usr/local/src. This way non-packaged source code can be easily distinguished from packaged and system managed source code.

Caution: You can still not be safe if some malformed custom built kernel module breaks your kernel.